There are a number of lithography processes which are well known in the art used in conjunction with manufacturing microelectronic devices. A typical lithography process involves aligning and transferring a pattern from a template using optics onto a partially processed substrate (e.g., wafer) that has been coated with a photoresist. The resist is then developed and the resist image is thereafter transferred into the underlying material typically by a chemical and/or thermal step such as, for example, dry/wet etch, sinter, implant, etc. This process is often repeated many times (e.g., between 15 to 20) during the course of building a complex integrated circuit.
The above processing steps can result in distortions being present in the wafer. Thus, wafer handling during processing is extremely important. The wafer handling subsystem is believed to be largely responsible for the throughput of the processing tool. Accordingly, the wafer handling should be designed to minimize sources of possible contamination. A difficulty from a processing standpoint relates to the incompatibility of an organic or aqueous solvent based coating solution and the enclosed equipment (e.g., a vacuum environment) used for processing substrates that have developed photo resist images (positive or negative) formed therein.
U.S. Pat. No. 5,665,527 to Allen et al. proposes a process for generating a negative tone resist image comprising the steps of coating a substrate with a film of a polymeric composition comprising a polymer, a photosensitive acid generator, and acid labile groups, imagewise exposing the film to radiation to generate free acid, and developing the image with critical fluid, e.g., carbon dioxide.
U.S. Pat. Application Ser. No. 2002/0119398 to DeSimone et al. describes CO2 processes, photoresists, polymers and photoactive compounds for positive and negative tone microlithography. Paragraph 45 therein states: “Any of the carbon dioxide-containing compositions may also include additional components, the selection of which is known to one skilled in the art. Exemplary components include, without limitation, aqueous and organic co-solvents, polymer modifiers, water, rheology modifiers, plasticizing agents, flame retardants, antibacterial agents, flame retardants, and viscosity reduction modifiers.”
V. Pham et al., Polymer Preprints 43, 885 (2002) describes positive-tone resists for supercritical CO2 processing.
Notwithstanding the above, there is a continued need in the art for processes for forming semiconductor devices that involve positive tone resists that may be used with carbon dioxide solvents.